The present invention relates to a data processing apparatus which allows a specific key to automatically perform a series of arithmetic operations for key codes respectively corresponding to a plurality of keys.
In a data processing apparatus applied to an electronic cash register, the following operation is required in a store which offers a 15% discount, as shown in FIG. 1. After pieces of sales data, "200" and "300" are sequentially entered by the numerical keys and the department keys respectively, the operator must sequentially press a subtotal key ST, numerical keys for a value 15, a discount key %-, and a cash key CA. However, in a case where the operator repeats the same operation for different customers, the key operation becomes inconvenient. Furthermore, if the operator forgets to press the subtotal key ST, a discount is not performed on the subtotal amount data, but on the department data amount (e.g., "300") which is entered immediately before the discount key CA is pressed. If the operator erroneously presses different numerical keys for a discount, a discount value may be mistakenly changed, resulting in great inconvenience.